Heart sound monitoring of pulmonary hypertension

ABSTRACT

A medical device system and method that includes receiving an A 2  heart sound signal from a first external acoustic sensor, receiving a P 2  heart sound signal from a second external acoustic sensor, determining at least one A 2  heart sound signal parameter from the A 2  heart sound signal, determining at least one P 2  heart sound signal parameter from the P 2  heart sound signal, and based on the at least one P 2  heart sound signal parameter, estimating pulmonary arterial pressure.

RELATED APPLICATION

The present application claims priority and other benefits from U.S.Provisional Patent Application Ser. No. 61/608,396, filed Mar. 8, 2012,entitled “HEART SOUND MONITORING OF PULMONARY HYPERTENSION”,incorporated herein by reference in its entirety.

TECHNICAL FIELD

The disclosure relates to the use of heart sound signals to monitorpulmonary hypertension.

BACKGROUND

A wide variety of medical devices are used for delivering a therapy ormonitoring a physiological condition related to a cardiac health withina patient. For example, implantable medical devices, such as cardiacpacemakers or implantable cardioverter defibrillators, providetherapeutic stimulation to the heart by delivering electrical therapysignals, such as pulses for pacing, or shocks for cardioversion ordefibrillation. In some cases, such an implantable medical device (IMD)may sense for intrinsic depolarizations of the heart, and control thedelivery of such signals to the heart based on the sensing.

In some cases, an IMD device includes sensors for detecting heart soundssignals in addition to electrical signals. As described in PublishedU.S. Patent Application 2010/0331903 to Zhang et al. entitled “HEARTSOUND SENSING TO REDUCE INAPPROPRIATE TACHYARRHYTHMIA THERAPY,”incorporated herein by reference in its entirety, heart sounds signalsare detected and used to determine whether the heart sounds are normalor abnormal. The heart sounds may also be used to confirm or reject anindication that therapy may be needed based on electrical signals.

Heart failure is a condition affecting thousands of people worldwide.Essentially, congestive heart failure occurs when the heart is unable topump blood at an adequate rate in response to the filling pressure. Aworsening heart failure condition may result in symptoms such ascongestion in the tissue, peripheral edema, pulmonary edema, andshortness of breath, and coughing. When heart failure is severe, it caneven lead to patient death.

Pulmonary hypertension is abnormally high blood pressure in the arteriesof the lungs. The right side of the heart of a patient with pulmonaryhypertension must work harder than normal to provide an adequate bloodsupply to the lungs. In patients with pulmonary hypertension the bloodvessels of the lungs have narrowed causing pressure build up. The extrawork the heart must do to force the blood through the vessels can resultin an enlarging of the right side of the heart. This may eventuallyresult in heart failure in the right side of the heart.

SUMMARY

In general, the disclosure is directed to using heart sounds to monitorfor pulmonary hypertension. In some examples, specific heart sounds,along with characteristics of the detected heart sound, are associatedwith the presence of pulmonary hypertension within a patient.

In one example, the disclosure is directed to a method comprisingreceiving an A2 heart sound signal from a first external acousticsensor; receiving a P2 heart sound signal from a second externalacoustic sensor; determining at least one A2 heart sound signalparameter from the A2 heart sound signal; determining at least one P2heart sound signal parameter from the P2 heart sound signal; and basedon the at least one P2 heart sound signal parameter, estimatingpulmonary arterial pressure.

In another example, the disclosure is directed to a system comprising atelemetry module configured to receive an A2 heart sound signal from afirst external acoustic sensor and a P2 heart sound signal from a secondexternal acoustic sensor. The system also comprising a processorconfigure to determine at least one A2 heart sound signal parameter fromthe A2 heart sound signal, determine at least one P2 heart sound signalparameter from the P2 heart sound signal, and estimate pulmonaryarterial pressure based on the at least one P2 heart sound signalparameter.

In another example, the disclosure is directed to a computer-readablemedium containing instructions. The instructions cause a programmableprocessor to receive an A2 heart sound signal from a first externalacoustic sensor; receive a P2 heart sound signal form a second externalacoustic sensor; determine at least one A2 heart sound signal parameterform the A2 heart sound signal; determine at least one A2 heart soundsignal parameter from the A2 heart sound signal; determine at least oneP2 heart sound signal parameter from the P2 heart sound signal; andbased on the at least one P2 heart sound signal parameter, estimatepulmonary arterial pressure.

In another example, the disclosure is directed to a system includingmeans for receiving an A2 heart sound signal from a first externalacoustic sensor; means for receiving a P2 heart sound signal from asecond external acoustic sensor; means for determining at least one A2heart sound signal parameter from the A2 heart sound signal; means fordetermining at least one P2 heart sound signal parameter from the P2heart sound signal; and means for, based on the at least one P2 heartsound signal parameter, estimating pulmonary arterial pressure.

The details of one or more examples consistent with this disclosure areset forth in the accompanying drawings and the description below. Otherfeatures, objects, and advantages of the disclosure will be apparentfrom the description and drawings, and from the claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a conceptual diagram illustrating an exemplary system thatacquires heart sound signals for use in detecting pulmonary hypertensionand heart failure in a patient.

FIG. 2 is a conceptual diagram illustrating another exemplary systemthat acquires heart sound signals for use in detecting pulmonaryhypertension and heart failure in a patient.

FIG. 3 is a block diagram illustrating an example system that includesan external device, such as server, and one or more computing devicesthat are coupled to external patch, an IMD and a programmer, as shown inFIG. 2, via a network.

FIG. 4 is a block diagram illustrating an example programmer forprogramming an external patch and an IMD.

FIG. 5 is a block diagram illustrating an example external patch.

FIG. 6 is a block diagram of an example IMD.

FIG. 7 is a block diagram illustrating an example configuration ofsignal analyzer.

FIG. 8 is a flow chart illustrating an example method consistent withthe present disclosure.

FIG. 9 is a flow chart illustrating another example method consistentwith the present disclosure.

FIG. 10 is a flow chart illustrating another example method consistentwith the present disclosure.

FIG. 11 is a conceptual diagram illustrating an exemplary external patchconsistent with the present disclosure.

DETAILED DESCRIPTION

As used herein, the term heart sound refers to a feature of a heartsound signal, such as the S1, S2, S3, or S4 heart sounds. There may bemultiple heart sounds, e.g., each of an S1, S2, S3 and S4 heart sound,for any given cardiac cycle or heart beat. In some examples, the medicaldevice classifies a heart beat or cardiac cycle as normal or abnormalbased on the classifications for one or more heart sounds detectedduring the heart beat or cardiac cycle. In such examples, the medicaldevice may confirm that a cardiac rhythm is treatable when one or moreheart beats are classified as abnormal, or withhold therapy when one ormore heart beats are classified as normal.

In general, heart sounds are associated with mechanical vibrations of apatient's heart and the flow of blood through the heart valves, and,thus, are highly correlated with pressure gradients across heart valvesand blood pressure. Heart sounds are not only due to vibrations of andpressure within the heart, but may be due to the entire cardiohemicsystem, e.g., blood, heart, great arteries, etc. Heart sounds recur witheach cardiac cycle and are separated and classified according to theactivity associated with the vibration. The first heart sound isreferred to as “S1,” and can be thought of as the vibration sound madeby the heart during closure of the atrioventricular (AV) valves, i.e.,the mitral valve and tricuspid valve. The S1 sound can sometimes bebroken down into the M1 sound, from the closing of the mitral valve, andthe T1 sound, from the closing of the tricuspid valve.

The second heart sound is referred to as “S2,” and results from theclosure of the semilunar valves, i.e., the pulmonary and aortic valves.The S2 heart sound can be thought of as marking the beginning ofdiastole. The S2 sound can also be broken down into component parts. TheP2 sound is from the closing of the pulmonary valve and the A2 sound isfrom the closing of the aortic valve. The third and fourth heart soundsare referred to as “S3” and “S4,” respectively, and can beconceptualized as related to filling of the ventricles during diastole.S3 is due to rapid filling of the ventricles and can occur when theventricular wall is not relaxed when a large volume of blood flows intothe ventricle from the atria. S4 is caused by blood rapidly filling intothe ventricles from the atria due to atrial contraction.

In some examples an acoustic sensor may also monitor lung sounds.Collected acoustic waveforms may be analyzed to evaluate respiratoryrate, depth of inhalation, and the like, and to determine whether one ormore abnormal breath sounds is present. In some examples, the some ofthe identified lung sounds may be associated with heart failure. Forexample an IMD or other computing device may determine whether theacoustic waveform indicates the presence of coughing, rales, rhonchi,stridor, or wheezing, as examples.

Rales are small clicking, bubbling, or rattling sounds in the lung.Rales are believed to occur when air opens closed air spaces within thelungs. Rales can be further described as moist, dry, fine, and coarse.Rhonchi are sounds that resemble snoring. Rhonci occur when air isblocked or its passage through large airways of the lungs becomesturbulent. Stridor is a wheeze-like sound heard when a person breathes.Usually stridor is due to a blockage of airflow in the windpipe(trachea) or in the back of the throat. Wheezes are high-pitched soundsproduced by narrowed airways. They can be heard when a person exhales.

Pulmonary hypertension is an increase in blood pressure in the pulmonaryartery, pulmonary vein, or pulmonary capillaries, together known as thelung vasculature. The increased blood pressure leads to shortness ofbreath, dizziness, fainting and other symptoms, which are exacerbated byexertion. Pulmonary hypertension may result in a decrease in exercisetolerance and can lead to heart failure. Pulmonary venous hypertensiontypically presents with shortness of breath while lying flat orsleeping. Pulmonary arterial hypertension, however, is usually notassociated with shortness of breath while lying flat.

Consistent with the present disclosure, a correlation between heartand/or lung sounds are used to monitor pulmonary hypertension, includingprogression and treatment. As discussed in this disclosure, two sensorsmay be used for detecting the A2 and P2 heart sounds separately. Thesensors can be subcutaneous, external, or a combination of both. In someexamples, a non-invasive patch sensor may be used to monitor at leastheart sounds. The external patch may concurrently monitor both A2(systemic blood pressure) and P2 (pulmonary blood pressure) heartsounds. The external patch may include at least two sensors, one formonitoring A2 heart sounds and one for monitoring P2 heart sounds. Insome examples, the use of an external patch may allow for a patient tobe monitored continuously or at regular intervals without the need forinvasive procedures to determine pulmonary arterial blood pressure.

In some examples, a patient may be directed to attach, using reusableadhesive, for example, a patch containing acoustic electrodes at apredetermined time of day. Heart sound and/or lung sounds may becollected while the electrodes are in place. In some examples, the A2and P2 heart sounds may be compared to historic A2 and P2 heart sounds.Changes in one or more characteristics of the heart sound signals mayindicate progression of pulmonary hypertension or heart failure. Forexample, an increase in the P2 heart sound amplitude may indicate anincrease in pulmonary pressure.

In some examples, the A2 heart sound may calibrated with a non-invasiveblood pressure measurement. In some examples, the relationship betweenthe P2 heart sound and the A2 heart sound may be used to track theprogression of, or identify the occurrence of, pulmonary hypertension.For example, if the A2 heart sound indicates that arterial bloodpressure is above a certain threshold and the P2 heart sound amplitudeis greater than the A2 heart sound, this may indicate that the patienthas pulmonary hypertension.

In some examples, the A2 and/or P2 heart sounds may be used to titratetreatment of pulmonary hypertension. In some examples, therapy fortreatment of pulmonary hypertension may be adjusted until the P2 heartsound falls below a certain predetermined threshold. The use of externalsensors allows for the monitoring of pulmonary pressure without the needfor invasive monitoring such as a pressure lead placed in the rightventricle or pulmonary artery. External sensors also allow formonitoring of pulmonary pressure outside of the clinical setting.

After taking proper medication, for example, to treat pulmonaryhypertension, the pulmonary vessels should be dilated. In some examples,the sound caused by blood flowing through the dilated blood vessel willbe different than the sound resulting from the blood flowing through theconstricted vessels of the patient with pulmonary hypertension. In someexamples, the sound after vessel dilation will include a higherfrequency sound that the constricted vessels. In some examples,monitoring the signal frequency of blood flow may estimate the efficacyof pulmonary hypertension therapy or progression.

In some examples, two acoustic sensors are used. The two acousticsensors are placed so that one is approximately over the left side ofthe heart and the other is approximately over the right side of theheart. The use of two acoustic sensors may simplify differentiationbetween the A2 and P2 heart sounds. In some examples, the two sensorsare designed to directionally collect A2 and P2 sounds, one each,concurrently. In some examples, the placement of the two sensors may bebased on the results of a patient chest X-ray, or other patient imagingtechnique, that indicate the aorta and pulmonary artery. One sensor isplaced over the aorta while the other is placed over the pulmonaryartery. In some examples, each sensor can be designed to confine soundwave detected to the appropriate acoustic waveform. Normal auscultationat either the aortic location or pulmonary location includes sound fromboth locations because the sound waves from the aortic valve and thepulmonary valve must both travel through the patient's body. In caseswhere the S2 splice is not obvious, it may be difficult to separate theA2 and P2 heart sounds. However, the use of two specifically designedacoustic sensors, one focused on the aortic value and one focused on thepulmonary valve, provides for greater ease in differentiating betweenthe A2 and P2 heart sounds.

In some examples, heart sounds, in particular the A2 and P2 heart soundsmay be used in conjunction with lung sounds and/or other signals such aselectrocardiogram (ECG) or impedance signals, to detect heart failure.For examples, when a heart sound signal is used with an ECG signal thatis collected by two ECG electrodes, different than the acoustic sensors,the ECG signal can provide information to help identify the S2 heartsound from heart sound signals as well as the interval separating the P2heart sound and the QRS wave. The interval separating the P2 heart soundand the QRS wave may also suggest the presence of pulmonaryhypertension. In some examples, and external acoustic sensor may aid inthe monitoring of heart failure progression. In particular, heart soundsmay be used to detect pulmonary hypertension induced heart failureprogression.

In some examples, timing of heart sound collection may be based ondetected lung sounds. For example, A2 and P2 heart sounds may becollected during a phase of no inspiration-expiration to avoid heartsound contamination by respiration sound. In some examples an ECG signalmay be used to help determine which portion of the heart sound signal tocollect. For example, heart sounds may be collected in a window of timeprior to the QRS interval to collect heart sound related to filling.Heart sound may also be collected post QRS interval to collect heartsound related to ejection.

FIG. 1 is a conceptual diagram illustrating an exemplary system 10 thatdetects heart sounds for use in detecting pulmonary hypertension andheart failure in patient 12. In particular, system 10 includes anexternal patch 16 with acoustic sensors 18 and 20. External patch 16 isplaced on patient 12 over sternum 22 so that acoustic sensor 18 over theright side of the heart 14 and acoustic sensor 20 is over the left sideof heart 14. This placement allows for acoustic sensor 18 to better pickup the sound of the aortic valve closing (heart sound A2) and acousticsensor 20 to better pick up the sound of the pulmonary valve closing(heart sound P2). In some examples, external patch 16 is placed so thatacoustic sensors 18 and 20 are located over spaces between the ribs.This also allows for better capture of the heart sounds. In someexamples, an optimal location for the two sensors may be determined byreferencing a chest X-ray film for the patient.

System 10 also includes a programmer 24. External patch 16 iscommunicatively coupled to programmer 24. In some examples, programmer24 takes the form of a handheld computing device, computer workstation,or networked computing device that includes a user interface forpresenting information to and receiving input from a user. A user, suchas a physician, technician, surgeon, electro-physiologist, or otherclinician, may interact with programmer 24 to retrieve physiological ordiagnostic information from external patch 16. In certain examplesvarious functions of the programmer 24 may be automated. A user may alsointeract with programmer 24 to program external patch 16, e.g., selectvalues for operational parameters of the IMD. For example, theoperational parameters may be selected automatically in response to oneor more acoustic cardiographic metrics. In other examples the functionof programmer 24 may be split between an external programmer and aninternal programmer within external patch 16.

External patch 16 and programmer 24 may communicate via wirelesscommunication using any techniques known in the art. Examples ofcommunication techniques may include, for example, low frequency orradiofrequency (RF) telemetry. Other techniques are also contemplated.In some examples, programmer 24 may include a programming head that maybe placed proximately to the patient's body near the IMD 16 implant sitein order to improve the quality or security of communication between IMD16 and programmer 24. In other examples, programmer 24 may be locatedremotely from IMD 16, and communicate with IMD 16 via a network. In someexamples, IMD 16 and programmer 24 may work with general networktechnology and functionality similar to that provided by the MedtronicCareLink® Network developed by Medtronic, Inc., of Minneapolis, Minn.

In some examples, programmer 24 may process heart sound signals receivedfrom external patch 16 to determine if a change in patient state hasoccurred. For example, programmer 24 may determine whether a patient haspulmonary hypertension based on A2 and P2 heart sounds. In someexamples, as discussed in more detail below with respect to FIG. 2,programmer 24 may receive one or more additional signals from animplantable medical device or other medical device that monitors othercardiac or lung activity. Programmer 24 may use the heart sounds signalscollected by external patch 16 in conjunction with other signals such aslung sound signals to determine whether a patient has pulmonaryhypertension induced heart failure.

FIG. 2 is a conceptual diagram illustrating an exemplary system 100 thatdetects heart sounds for use in detecting pulmonary hypertension andheart failure in patient 12. System 100 include external patch 16,programmer 24, implantable medical device (IMD) 26 and blood pressuremonitor 28. In some examples, system 100 may be used to calibratedetected A2 heart sounds with arterial blood pressure detected withblood pressure monitor 28. In addition, system 100 includes an IMD 26that may be used to provide electrical stimulation therapy to heart 14of patient 12. In some examples, IMD 26 may be a leadless device. IMD 26may include a plurality of housing electrodes. The housing electrodesmay be formed integrally with an outer surface of a hermetically sealedhousing of the IMD, or otherwise be coupled to the housing. The housingelectrodes may be defined by uninsulated portions of a portion, e.g., anoutward facing portion of the housing of IMD 26. In some examples, thehousing of IMD 26 may include an array of electrodes. For example, IMD26 may include a 4 or 8 electrode array. Programmer 24 may modifytherapy parameters for therapy provided by IMD 26 based on heart soundssignals collected by acoustic sensor 18 and 20, on a blood pressuresignal from blood pressure monitor 28, or on ECG, ECG, or acousticsignals detected by IMD 26. In other examples, IMD 16 may be a drug pumpcontaining medicines for treatment of pulmonary hypertension or othercardiac disease which may be controlled via close-loop feedback based onA2 and P2 heart sound signals or other signals collected by the system.

FIG. 3 is a block diagram illustrating an example system that includesan external device, such as server 34, and one or more computing devices38A-38N that are coupled to external patch 16, IMD 26 and programmer 24shown in FIG. 2 via a network 32. Network 32 may be generally used totransmit diagnostic information (e.g., an indication of pulmonaryhypertension) from programmer 24 to a remote external computing device.In some examples, the heart sounds and/or lung sounds signals may betransmitted to an external device for processing.

In some examples, the information transmitted by external patch 16and/or IMD 26 may allow a clinician or other healthcare professional tomonitor patient 12 remotely. In some examples, external patch 16 may useits telemetry module 52 (discussed in more detail below with respect toFIG. 5) to communicated with programmer 24 via a first wirelessconnection, and to communicate with an access point 40 via a secondwireless connection, e.g., at different times. In the example of FIG. 3,access point 40, programmer 24, IMD 26, server 34, and computing devices38A-38N are interconnected, and able to communicate with each other,through network 32. In some cases one or more of access point 40,programmer 24, server 34, and computing devices 38A-38N may be coupledto network 32 via one or more wireless connections. External patch 16,IMD 26, programmer 24, server 34 and computing devices 38A-38N may eachcomprise one or more processors, such as one or more microprocessors,DSPs, ASICs, FPGAs, programmable logic circuitry, or the like, that mayperform various functions and operations, such as those describedherein.

Access point 40 may comprise a device that connects to network 32 viaany of a variety of connections, such as telephone dial-up, digitalsubscriber line (DSL), or cable modem connections. In other examples,access point 40 may be coupled to network 32 through different forms ofconnections, including wired or wireless connections. In some examples,access point 40 may be co-located with patient 12 and may comprise oneor more programming units and/or computing devices (e.g., one or moremonitoring units) that may perform various functions and operationsdescribed herein. For example, access point 40 may include ahome-monitoring unit that is co-located with patient 12 and that maymonitor the activity of external patch 16 and IMD 26. In some examples,server 34 or computing devices 38 may control or perform any of thevarious functions or operations described herein, e.g., determine, basedon heart sounds, whether the patient has pulmonary hypertension.

In some cases, server 34 may be configured to provide a secure storagesite for archival of diagnostic information (e.g., occurrence of apulmonary hypertension and attendant circumstances such as patientposture and activity level) that has been collected and generated fromexternal patch 16, IMD 26 and/or programmer 24. Network 32 may comprisea local area network, wide area network, or global network, such as theInternet. In some cases, programmer 24 or server 34 may assemblepulmonary hypertension and heart failure information in web pages orother documents for viewing by trained professionals, such asclinicians, via viewing terminals associated with computing devices 38.The system of FIG. 3 may be implemented, in some aspects, with generalnetwork technology and functionality similar to that provided by theMedtronic CareLink® Network developed by Medtronic, Inc., ofMinneapolis, Minn.

In the example of FIG. 3, external server 34 may receive heart soundinformation from external patch 16 and lung sound information from IMD26 via network 32. Based on the heart sound information received,processor(s) 36 may preform one or more of the functions describedherein with respect to signal analyzer 46 and processor 44 (describedwith respect to FIG. 4, below). In some examples, cardiac signalsincluding ECG and heart sounds signals are transmitted to an externaldevice and the external device, such as server 34, processes the signalsto determine whether a pulmonary hypertension or heart failure hasoccurred.

FIG. 4 is a block diagram illustrating an example programmer 24 forprogramming external patch 16 and IMD 26. Programmer 24 may be providedin the form of a handheld device, portable computer or workstation thatprovides a user interface to a physician or patient. In the example ofFIG. 4, programmer 24 includes processor 44, memory 48, telemetryinterface 42, user interface 50, and signal analyzer 46. In general, auser, i.e., a physician or clinician uses programmer 24 to program andcontrol IMD 26. In addition, programmer 24 may be used to determine ifpatient 12 has developed pulmonary hypertension or heart failure basedon information collected by external patch 16 and/or IMD 26.

In the example of FIG. 4, a user interacts with processor 44 via userinterface 50 in order access diagnostic and program informationregarding patient 12 stored in memory 48. The user may also interactwith processor 44 via user interface 50 in order to modify programsettings for external patch 16 and/or IMD 26. User interface 50 may be agraphical user interface (GUI). The user interface 50 may also includeone or more input media. In put media may include, for example, akeyboard or a touchscreen. In addition, the user interface may includelights, audible alerts, or tactile alerts. Processor 44 may include amicroprocessor, a microcontroller, a DSP, an ASIC, an FPGA, or otherequivalent discrete or integrated logic circuitry.

In some examples, processor 44 may control external patch 16 and/or IMD26 via telemetry module 42. For example, processor 44 may be used todetermine when external patch 16 collects heart sound signals fromacoustic sensors 18 and 20. Processor 44 may also modify one or moretherapy parameters used to delivery therapy by IMD 26 in response toheart sound signals collected by external patch 16. In particular,processor 44 may transmit program signal to external patch 16 or IMD 26via telemetry module 42.

Signal analyzer 46 receives an electrical signal that was generated byacoustic sensor 18 or 20 and transmitted via telemetry module 52 ofexternal patch 16 to telemetry module 42. In one example, signalanalyzer 46 may process the sensor signals generated by acoustic sensors18 and 20 to detect heart sounds. Signal analyzer 46 may also generateone or more acoustic cardiographic metrics indicative of heartperformance based on the characteristics of one or more of the detectedheart sounds. For example, signal analyzer 46 may determine theamplitude of heart sounds A2 and P2. Signal analyzer 46 may generate anenvelope signal and apply an algorithm that uses an adaptively decayingthreshold, to detect events within the envelope signal. Signal analyzer46 extracts event features from the detected events, and determines oneor more heart sound parameters based on the features. In some examples,signal analyzer 46 may process the signal from acoustic sensor 18 inorder to extract features of heart sound P2 and process the signal fromacoustic sensor 20 in order to extract features of heart sound A2.

In some examples, signal analyzer 46 may also process sensor signals fora lung sound sensor 60 in IMD 26. As with the electrical signals fromacoustic sensors 18 and 20 of external patch 16, signal analyzer 46 mayprocess the lung sound signal to generate an envelope signal and applyan algorithm that uses an adaptively decaying threshold, to detectevents within the envelope signal. Signal analyzer 46 extracts eventfeatures from the detected events, and determines one or more lung soundparameters based on the features Signal analyzer 46 may determine if oneor more of the lung sound parameters indicate the presence of, orprogression of, heart failure within patient 12.

Signal analyzer 46 may provide an indication of a determination of heartfailure or pulmonary hyper tension to processor 44. In some examples,signal analyzer 46 may provide an indication of the heart sound signalparameter and the lung sound signal parameters derived from the signalsreceived from external patch 16 and IMD 26. The operation of signalanalyzer 46 in accordance with these example methods is described ingreater detail with respect to FIGS. 8-10. In any case, a heart and/orlung sound based indication of patient status may be output to processor44, which may allow, modify or withhold therapy based on patient status.Processor 44 or signal analyzer 46 may store the heart sound signalparameters and lung sound signal parameters in memory 48. In someexamples, processor 44 may store the determination of patient statusalong with any changes made to therapy based on the patient status inmemory 48.

Although processor 44 and signal analyzer 46 are illustrated as separatemodule in FIG. 4, processor 44 and signal analyzer 46 may beincorporated in a single processing unit. Signal analyzer 46 may be acomponent of or a module executed by processor 44.

Furthermore, the components of and functionality provided by signalanalyzer 46 are described herein with respect to examples in whichsignal analyzer 46 is located within programmer 24. However, it isunderstood, and discussed in more detail below, that any one or moresignal analyzers 46 may be individually or collectively provided by anyone or more devices, such as IMD 26, external patch 16, or server 34, toindividually or collectively provide the functionality described herein.

Memory 48 includes computer-readable instructions that, when executed byprocessor 44, cause programmer 24 to perform various functionsattributed to programmer 24 and processor 44 herein. Memory 48 mayinclude any volatile, non-volatile, magnetic, optical, or electricalmedia, such as a random access memory (RAM), read-only memory (ROM),non-volatile RAM (NVRAM), electrically-erasable programmable ROM(EEPROM), flash memory, or any other digital or analog media. Memory 48may also store one or more therapy programs or parameters to be executedby IMD 26. Memory 48 may also store instructions regarding when externalpatch 16 collects heart sound signals.

Telemetry module 42 includes any suitable hardware, firmware, softwareor any combination thereof for communicating with another device, suchas external patch 16 (FIG. 1). Under the control of processor 44,telemetry module 42 may send downlink telemetry to and receive uplinktelemetry from external patch 16 and/or IMD 26 with the aid of anantenna, which may be internal and/or external. Information whichprocessor 44 may transmit to IMD 26 via telemetry module 42 may includean indication of a change in disease state of the heart, or a change inprogramming to change one or more therapy parameters. The indication maybe based heart and/or lung sounds.

FIG. 5 is a block diagram illustrating an example external patch 16.External patch 16 includes acoustic sensors 18 and 20, processor 51 andtelemetry module 52. In some examples, external patch 16 may include oneor more additional sensors 19. External patch 16 may also include apower source, not shown. External patch 16 may include a reusableadhesive. The adhesive may be used to hold external patch 16 in place onpatient 12 as shown in FIGS. 1 and 2. In some examples, external patch16 is located on patient 12 so that acoustic sensor 18 is locatedapproximately above the right side of heart 14 and acoustic sensor 20 islocated approximately above the left side of heart 14. In certain morespecific examples, acoustic sensor 18 is located approximately above theaortic valve of heart 14 and acoustic sensor 20 is located approximatelyabove the pulmonary value of heart 14.

Acoustic sensor 18 generates an electrical signal based on sound orvibration, e.g., sensed heart sounds of patient 12, and may beimplemented as a piezoelectric sensor, a microphone, an accelerometer,or other type of acoustical sensor. In some examples, acoustic sensor 18may comprise one or more sensors. For example, acoustic sensor 18 mayinclude multiple accelerometer devices. Information obtained fromacoustic sensor 18 may be used to aid in the detection of pulmonaryhypertension and heart failure.

Acoustic sensor 20 also generates an electrical signal based on sound orvibration, e.g., sensed heart sounds of patient 12, and may beimplemented as a piezoelectric sensor, a microphone, an accelerometer,or other type of acoustical sensor. In some examples, acoustic sensor 20may comprise one or more sensors. For example, acoustic sensor 20 mayinclude multiple accelerometer devices. Information obtained fromacoustic sensor 20 may be used to aid in the detection of pulmonaryhypertension and heart failure.

In some examples, the signals collected by acoustic sensor 18 andacoustic sensor 20 may be filtered at different frequencies. Thefiltering may be done by processor 51. The location difference betweenthe two sensors may also be used to help differentiate between the A2and P2 sounds in the collected heart sound signals.

In some examples, acoustic sensors 18 and 20 may detect an acousticwaveform that includes both heart sounds and lung sounds. Processor 51may amplify the signals from acoustic sensors 18 and 20 prior totransmission via telemetry module 52. In some examples, processor 51 mayuse band-pass filters to separate heart sound signals from lung soundsignals. In some examples, the acoustic waveform may be transmitted toprogrammer 24 via telemetry module 52 for processing. Processor 44 ofprogrammer 24 may use bandpass filters to separate the heart soundsignals from the lung sound signals. In some examples, processor 51 mayperform a portion of the signal processing with the other portion of thesignal processing performed by processor 44 of programmer 24. Forexample, processor 51 may separate the heart sound signals from the lungsound signals while processor 44 detects individual heart sounds withinthe separated heart sound signal.

In some examples, external patch 16 may include one or more additionalsensors 19. For example, the sensor 19 may be an electrode configured todetect ECG signals. In other examples, the sensor 19 may be one or moreof an additional acoustic sensor, a temperature sensor or an activitylevel sensor, for example. The signal from sensor 19 may be processed byprocessor 51 before being transmitted to external programmer 24 or IMD26 via telemetry module 52.

FIG. 6 is a block diagram of an example IMD 26. IMD 26 may include aprocessor 54, a memory 56, a telemetry module 48, a sound sensor 60, asignal analyzer 62 an activity/posture sensor 64, a signal generator 66and a sensing module 68. Memory 56 includes computer-readableinstructions that, when executed by processor 54, cause IMD 26 andprocessor 56 to perform various functions attributed to IMD 26 andprocessor 54 herein. Memory 56 may include any volatile, non-volatile,magnetic, optical, or electrical media, such as a random access memory(RAM), read-only memory (ROM), non-volatile RAM (NVRAM),electrically-erasable programmable ROM (EEPROM), flash memory, or anyother digital or analog media.

Processor 54 may include any one or more of a microprocessor, acontroller, a digital signal processor (DSP), an application specificintegrated circuit (ASIC), a field-programmable gate array (FPGA), orequivalent discrete or analog logic circuitry. In some examples,processor 54 may include multiple components, such as any combination ofone or more microprocessors, one or more controllers, one or more DSPs,one or more ASICs, or one or more FPGAs, as well as other discrete orintegrated logic circuitry. The functions attributed to processor 54herein may be embodied as software, firmware, hardware or anycombination thereof. Generally, processor 54 controls signal generator66 to deliver stimulation therapy to heart 14 of patient 12 according toa selected one or more of therapy programs or parameters, which may bestored in memory 56. As an example, processor 54 may control signalgenerator 66 to deliver electrical pulses with the amplitudes, pulsewidths, frequency, or electrode polarities specified by the selected oneor more therapy programs or parameters.

Signal generator 66 is configured to generate and deliver electricalstimulation therapy to patient 12. As shown in FIG. 5, signal generator66 is electrically coupled to electrodes 108, e.g., via conductors. Insome examples, not shown in FIG. 2, IMD 16 may connect to one moreleads. In some examples one or more electrodes 108 may be on the housingof IMD 26. For example, signal generator 66 may deliver pacing,defibrillation or cardioversion pulses to heart 14 via at least two ofelectrodes. In some examples, signal generator 66 delivers stimulationin the form of signals other than pulses such as sine waves, squarewaves, or other substantially continuous time signals.

Signal generator 66 may include a switch module (not shown) andprocessor 54 may use the switch module to select, e.g., via adata/address bus, which of the available electrodes are used to deliverthe electrical stimulation. The switch module may include a switcharray, switch matrix, multiplexer, or any other type of switching devicesuitable to selectively couple stimulation energy to selectedelectrodes. Electrical sensing module 68 monitors electrical cardiacsignals from any combination of electrode 108. Sensing module 68 mayalso include a switch module which processor 54 controls to select whichof the available electrodes are used to sense the heart activity,depending upon which electrode combination is used in the currentsensing configuration.

Sensing module 68 may include one or more detection channels, each ofwhich may comprise an amplifier. The detection channels may be used tosense the cardiac signals. Some detection channels may detect events,such as R-waves or P-waves, and provide indications of the occurrencesof such events to processor 54. One or more other detection channels mayprovide the signals to an analog-to-digital converter, for conversioninto a digital signal for processing or analysis by processor 54.

For example, sensing module 68 may comprise one or more narrow bandchannels, each of which may include a narrow band filteredsense-amplifier that compares the detected signal to a threshold. If thefiltered and amplified signal is greater than the threshold, the narrowband channel indicates that a certain electrical cardiac event, e.g.,depolarization, has occurred. Processor 54 then uses that detection inmeasuring frequencies of the sensed events.

In one example, at least one narrow band channel may include an R-waveor P-wave amplifier. In some examples, the R-wave and P-wave amplifiersmay take the form of an automatic gain controlled amplifier thatprovides an adjustable sensing threshold as a function of the measuredR-wave or P-wave amplitude. Examples of R-wave and P-wave amplifiers aredescribed in U.S. Pat. No. 5,117,824 to Keimel et al., which issued onJun. 2, 1992 and is entitled, “APPARATUS FOR MONITORING ELECTRICALPHYSIOLOGIC SIGNALS,” and is incorporated herein by reference in itsentirety.

In some examples, sensing module 68 includes a wide band channel whichmay comprise an amplifier with a relatively wider pass band than thenarrow band channels. Signals from the electrodes that are selected forcoupling to the wide-band amplifier may be converted to multi-bitdigital signals by an analog-to-digital converter (ADC) provided by, forexample, sensing module 68 or processor 54. Processor 54 may analyze thedigitized version of signals from the wide band channel. Processor 54may employ digital signal analysis techniques to characterize thedigitized signals from the wide band channel to, for example, detect andclassify the patient's heart rhythm. For example, processor 54 maydetect the timing of the QRS wave of patient 12.

IMD 26 also includes lung sound sensor 60, signal analyzer 62 andactivity sensor 64. Lung sound sensor 60 generates an electrical signalbased on sound or vibration, e.g., sensed heart sounds of patient 12,and may be implemented as a piezoelectric sensor, a microphone, anaccelerometer, or other type of acoustical sensor. In some examples,lung sound sensor 60 may comprise more than one sensor. For example,lung sound sensor 60 may include multiple accelerometer devices.Activity sensor 64 may also comprise one or more accelerometers.Information obtained from lung sound sensor 60 and activity sensor 64may be used to provide a risk assessment with regard to worsening heartfailure. In some examples, signals from the lung sound sensor 60 andactivity sensor 64 are provided to signal analyzer 62 and, based oninformation extracted from the signals, an assessment of pulmonaryhypertension or heart failure may be made.

In the illustrated example of FIG. 6, lung sound sensor 60 is enclosedwithin the housing of IMD 26. In other examples, lung sound sensor 60may be located on a lead that is coupled to IMD 26 or may be implementedin a remote sensor that wirelessly communicates with IMD 26. In any caselung sound sensor 60 is electrically or wirelessly coupled to circuitrycontained within IMD 26.

Signal analyzer 62 receives the electrical signal generated by lungsound sensor 60. In one example, signal analyzer 62 may process thesensor signal generated by lung sound sensor 60 to detect lung soundsand respiratory characteristics such as inspiration, expiration,respiratory rate, depth of inspiration, and/or the presence of a coughor other respiratory anomalies such as rales, rhonci, stridor orwheezing. In some examples, signal analyzer 62 may also receiveelectrical signals generated by acoustic sensors 18 and 20. Signalanalyzer 62 may process both the acoustic signals from the acousticsensors 18 and 20 of external patch 16 and the lung sound sensor 60 ofIMD 26. Signal analyzer 62 may process the signals to determine whetherpulmonary hypertension or heart failure are present in patient 12 asdiscussed below with respect to FIGS. 8-10.

Although processor 54 and signal analyzer 62 are illustrated as separatemodules in FIG. 6, processor 54 and signal analyzer 62 may beincorporated in a single processing unit. Signal analyzer 62, and any ofits components, may be a component of or a module executed by processor54.

Furthermore, the components of and functionality provided by signalanalyzer 62 are described herein with respect to examples in whichsignal analyzer 62 is located within IMD 26. However, it is understoodthat any one or more signal analyzers 62 may be individually orcollectively provided by any one or more devices, such as IMD 26 andprogrammer 24, to individually or collectively provide the functionalitydescribed herein. Programmer 24 may receive electrical signals generatedby lung sound sensor 60 from IMD 26 in examples in which programmer 24includes signal analyzer 46.

As illustrated in FIG. 6, IMD 26 may also include an activity and/orposture sensor 64. Activity and/or posture sensor 64 may, for example,take the form of one or more accelerometers, or any other sensor knownin the art for detecting activity, e.g., body movements or footfalls, orposture. In some examples, activity and/or posture sensor 64 maycomprise a three-axis accelerometer. In some examples, lung sound sensor60 and activity and/or posture sensor 64 may comprise one or more commonaccelerometers. As will be described in greater detail below withreference to FIGS. 8-10, processor 54 or signal analyzer 62 may usesignals from activity and/or posture sensor 64 in various aspects of theheart sound and lung sound analysis. For example, processor 54 maydirect acoustic sensors 18 and 20 to collect heart sound signals duringperiods were the activity level of patient 12 is below a predeterminedthreshold.

Telemetry module 88 includes any suitable hardware, firmware, softwareor any combination thereof for communicating with another device, suchas programmer 24 or external patch 16 (FIG. 2). Under the control ofprocessor 54, telemetry module 58 may receive downlink telemetry fromand send uplink telemetry to programmer 24 with the aid of an antenna,which may be internal and/or external. In some examples, processor 54may transmit directions to external patch 16 and receive acousticsignals for processing by processor 54 or signal analyzer 63. Processor54 may also transmit signals, e.g., ECG or ECG signals, produced bysensing module 68 and/or signals by lung sound sensor 60 to programmer24.

FIG. 7 is a block diagram illustrating an example configuration ofsignal analyzer 62. Although described as signal analyzer 62 of IMD 26,signal analyzer 46 functions in a similar manner. As illustrated in FIG.7, signal analyzer 62 may include an envelope extractor 90, eventdetector 92, feature module 94, and indication module 96.

Envelope extractor 90 receives one or more electrical signals fromacoustic sensors 18 and 20 and/or lung sound sensor 60. Each electricalsignal may be digitized and parsed into segments of predeterminedlength. As an example, the electrical signal generated by lung soundsensor 60 may be sampled at 200 Hertz (Hz) rate and parsed into segmentsincluding 100 or more sample points. Generally, envelope extractor 90processes the received signal to extract an envelope, i.e., generate anenvelope signal from the received signal.

In some examples envelope extractor 90 band pass filters, rectifies andsmoothes the sensor signal before extracting the envelope signal. Forexample, envelope extractor 90 may include a high pass filter, e.g., a40 Hz high pass filter, and a low pass filter, such as a 70 Hz low passfilter, to remove unwanted signal components from the heart sound sensorsignal. In some examples a first order infinite impulse response (IIR)high pass filter with a cutoff frequency of 40 Hz and a third order IIRlow pass filter with a cutoff of 70 HZ may be used. In some examples aband-pass filter with a 20 Hz high pass filter and a 70 Hz low passfilter is used. In some examples, analog filtering of the heart soundsensor signal may additionally or alternatively be performed prior todigitization of the signal and receipt by envelope extractor 90. Asdiscussed above, IMD 26 may include analog-to digital conversioncircuitry. The filters used for each of the electrical signals fromacoustic sensors 18 and 20 and lung sounds sensor 60 may differ. The useof different filters may allow for different information of interest tobe extracted from each signal. In some examples, the frequency of theheart sound signal may be separated into different bands by hardware orsoftware filtering. For example, the bands may by 10-100 Hz, 100-1000Hz, 1000-10,000 Hz, etc. Normal heart sounds have a frequency between10-200 Hz. In some examples, where disease state is present, the heartsounds may have a frequency above the 10-200 Hz range. For normal heartsounds the frequency of heart sound S1 is lower than heart sound S2. Inaddition the frequency of respiration rate is much lower (1-5 Hz) thannormal heart sounds. This may be helpful in filtering out respirationeffects.

In some examples, filtering may be used to detect particular respiratorysounds. For example, in detecting wheezing, a band-pass filter may beused to isolate the sounds resulting from wheezing. Wheezes aregenerally a continuous sound that can be characterized by both pitch andduration. The dominate frequency of a wheeze may be approximately 400Hz. Wheezes generally have a duration of greater than 100 millisecondsIn addition, both the fundamental and harmonic frequencies are greaterthan 100 Hz. Rhonchi is a low pitched wheeze with a duration of greaterthan 100 milliseconds and a frequency of greater than 300 Hz. Thedominant frequency in the power spectrum of rhonchi is approximately 100Hz. Crackles, on the other hand, are generally short and discontinuoussounds with a duration of less than 20 milliseconds. The differentcharacteristics of known respiratory sounds may be used to determineappropriate filtering and detection of abnormal respiratory sounds.

Envelope extractor 90 may also, in some examples, include rectificationcircuitry and circuitry that sums the rectified signal with left-shiftedand right-shifted rectified signals in order to smooth the rectifiedsignal. In this manner, envelope extractor may approximately apply ananalytic function transform to the signal for envelope extraction. Insome examples, envelope extractor 90 may use other methods to generatethe envelope signal, such as the normalized Shannon Energy, true Hilberttransform, or rectifying the derivative of the signal followed by movingwindow integration of the rectified derivative. In such examples,envelope extractor 90 extracts or generates the envelope signal of theprocessed signal, i.e., the band pass filtered, rectified, and smoothedsignal. Extraction of the envelope signal may further includeapplication of a box-car filter, such as a 16 point box-car filter, tothe band pass filtered, rectified, and smoothed signal. Envelopeextractor 90 outputs the envelope signal to event detector 92.

Event detector 92 utilizes an algorithm to detect various events withinthe envelope signal. The event detector 92 may be different for eachtype of electrical signal received. In some examples the event detector92 identifies heart sounds as well as lung sounds within each signalsenvelope to aid in the differentiation between heart sounds and lungssounds in each signal. Generally, event detector 92 identifies the localmaximums of the envelope signal. In order to identify the localmaximums, event detector 92 may utilize an adaptively decayingthreshold. The adaptively decaying threshold may be determined based onone or more of the running average of detected heart sound and/or coughamplitudes, the running average of the envelope signal amplitude, andthe mean heart sound-to-heart sound or cough-to-cough interval. Eventdetector 92 compares the envelope signal to the adaptively decayingthreshold to identify the local maximums. Event detector 92 may storemarkers, referred to as “event markers,” for the identified localmaximums within memory 72 or provide the event markers directly tofeature module 94. Feature module 94 extracts features of the detectedevents.

Feature module 94 may process the heart sounds signal in the frequencyor time domain. In some examples, feature module 94 may confirm that anevent detected by event detector 92 corresponds to the A2 heart sound,the P2 heart sound, or an identifiable lung sound, such as a cough. Insome examples, feature module 94 may extract information from the heartsounds signal regarding the characteristics of a cough, for example. Insome examples, feature module 94 may both confirm that an event detectedby event detector 92 corresponds to a cough and extract information fromthe heart sounds signal regarding the characteristics of the cough.Similarly, feature module may both confirm that the event detected byevent detector 92 corresponds to the A2 heart sound and extractinformation from the acoustic signal regarding the characteristics ofthe A2 heart sound. In examples where the feature module 94 extractsfeatures in the frequency domain, feature module 94 may extract featuresincluding mean or median frequency, high frequency components, lowfrequency components, and high/low frequency components energy ratio. Insome examples where feature module 94 extracts features of the timedomain, feature module 94 may extract information regarding morphologyof the A2 or P2 heart sound. Feature module 94 may extract informationregarding duration and frequency of lung sound episodes orrepetitiveness of coughing sounds episodes. Feature module 94 may alsodetermine the depth a breath or the depth of an abnormal breathing soundsuch as a cough.

In some examples, various features may be determined based on comparisonto a template. In some examples, various features may be determinedusing template matching schemes that compare detected lung soundanomalies to template lung sound anomalies, such as a wavelet templatematching scheme or a “bounded template” matching scheme. An examplewavelet template matching scheme is disclosed in U.S. Pat. No. 6,393,316issued to Jeff Gillberg. An example bounded template matching scheme isdisclosed in US Publication No. 20100185109, entitled “A BlurredTemplate Approach for Arrhythmia Detection,” by Xin Zhang, Mark Brown,Xusheng Zhang, and Jeff Gillberg.

In some examples, template lung sound anomalies used for determiningvarious features of the lung sound anomaly such as depth of the breath.In some examples, template anomalies may be lung sounds that weremeasured during a baseline interval of the patient with no breathinganomaly was present. That is, the template lung sounds may be obtainedfrom patient 12 in an identified or predetermined time period duringwhich the patient is known to have either a period without a lung soundanomaly present or a particular lung anomaly is known to be present. Insome examples, memory 72 stores lung sounds signals collected duringbreathing anomalies having specific characteristics as observed by thepatient 12 or a physician.

In some examples, feature module 94 may compare detected A2 or P2 heartsounds to predetermined thresholds or to each other. For example,feature module 94 may compare the amplitude of the P2 heart sound to astored threshold amplitude associated with a pulmonary pressureindicative of pulmonary hypertension. In some examples, feature module94 may compare the amplitude of the detected A2 and P2 heart sounds forthe same heart beat with each other to determine whether the P2 heartsound amplitude is greater than the A2 heart sound.

In some examples, feature module 94 may load different templatesdepending upon information from the activity/posture sensor 64. Forexample, in situations where the activity sensor 64 indicates that thepatient 12 is laying down the events may be compared to a differenttemplate than when patient 12 when the patient is propped up at anangle, and yet another template when the patient 12 is standing.

Indication module 96 receives information regarding various eventfeatures from feature module 94 and an activity signal from activitysensor 64. Based on the information from feature module 94 and activitysensor 64, indication module 96 may generate an indication a patient haspulmonary hypertension, or heart failure.

In some examples, the indication is provided to processor 54. Processor54 may modify the treatment provided to a patient based on a changeinpatient status or heart failure severity. In some examples, processor54 may provide the indication to programmer 54 so that therapy such asdrug therapy may be initiated or changed based on the indication ofpulmonary hypertension. In some examples, an indication of pulmonaryhypertension may incorporate information from activity sensor 64. Forexample, an indication of the degree of hypertension may be tempered bya concurrent indication of high activity.

FIG. 8 is a flow chart illustrating an example method consistent withthe present disclosure. External patch 16 and/IMD 26 monitor heart andlung sounds (70) using acoustic sensors 18 and 20 and/or lung soundsensor 60. In some examples, the acoustic sensor 18 and 20 may be usedto monitor both heart sounds and lung sounds. Signal analyzer 46 ofprogrammer 24 or signal analyzer 62 of IMD 26 determine heart sound andlung sound parameters (72). Heart sound parameters may include, forexample, heart sounds S1, S2, S3, and S4, length of the split betweenheart sounds A2 and P2, amplitude of heart sound A2, amplitude of heartsound P2, length of heart sound A2, length of heart sound P2, loudnessof the A2 and P2 heart sounds, and the power spectrums of the A2 and P2heart sounds. Processor 54 analyzes the P2 heart sound parameters for apulmonary hypertension signature (74). In some examples, the pulmonaryhypertension signature may be a P2 sound amplitude above a predeterminedthreshold. In some examples, the pulmonary hypertension signature may bea P2 sound amplitude that is greater than the A2 sound amplitude. Otherpulmonary hypertension signatures may include changes in the intervalbetween A2 and P2, valve regurgitation, heart sound frequency changes,or deviation of the P2 heart sound from a baseline P2 heart sound. Insome examples, the heart sound frequency changes may represent valvestiffness. Processor 54 determines if a pulmonary hypertension signaturehas been detected (78). If no pulmonary hypertension signature has beendetected then acoustic sensors 18 and 20 continue to monitor patientheart sounds. Signal analyzer 63 analyzes lung sounds parameters for oneor more heart failure signatures (76). In some examples the heartfailure signature may be a change in resting respiratory rate. In someexamples, the heart failure signature may crackles in the lung sounds orbreathlessness. In some examples, the heart failure signature may bebased on lung sounds in conjunction with heart sounds and/or an ECGsignal. For example the heart failure signature may be in increase inthe QRS-S1 interval, a decrease in S1 amplitude, or the appearance ofthe S3 heart sound. Processor 54 then determines if a heart failuresignature has been detected (80). If no heart failure signature isdetected, then IMD 26 and/or patch 16 continue to monitor the heart andlung sounds of patient 12.

If a pulmonary hypertension signature is detected (78), processor 54determines if both a heart failure signature and a pulmonaryhypertension signature have been detected (82). If a pulmonaryhypertension signature has been detected but a heart failure signaturehas not been detected processor 54 provides an indication that pulmonaryhypertension treatment should begin (86). In some examples, theindication of pulmonary hypertension is provided to programmer 24.Programmer 24 may provide an alert to patient 12 indicating the need tocheck in with his or her physician regarding treatment of pulmonaryhypertension. The physician may in turn start patient 12 on medicine totreat the pulmonary hypertension. In some examples, the indication ofpulmonary hypertension may be provided to a drug pump. The drug pump mayprovide a dose of medication to patient 12 based on the level ofpulmonary hypertension present. If both a pulmonary hypertensionsignature and a heart failure signature are detected, then processor 54provides an indication that both pulmonary hypertension treatment andheart failure treatment are need. In some examples, the heart failuretreatment may include modification to a current cardiac pacing program.

If a heart signature is detected (80), processor 54 determines if both aheart failure signature and a pulmonary hypertension signature have beendetected (82). If a heart failure signature is detected but a pulmonaryhypertension signature is not detected, then processor 54 provides anindication that heart failure treatment is needed (88). In someexamples, the heart failure signature may indicate a change in theseverity of a patient's heart failure. The indication may includeinformation regarding how big a change in severity has occurred.Processor 54 may modify one or more parameters of a current treatmentprogram in response to the indication of heart failure. For example,processor 54 may modify one or more parameters of a current cardiacpacing program. In examples where IMD 26 is a drug pump, changes may bemade to drug dosage. In other examples, a patient may be placed on oralmedication or altered to the need to take a particular medication. Othertherapeutic measures taken in response to an indication of heart failuremay include neuromodulation. In some examples, the indication of a needfor heart failure treatment may be provided to a physician viaprogrammer 24. The physician may manually change one or more treatmentparameters. If both a heart failure signature and a pulmonaryhypertension signature are detected, then indications of both areproduced. Changes in patient treatment may occur in order to treat bothpulmonary hypertension and heart failure (84).

FIG. 9 is a flow chart illustrating another example method consistentwith the present disclosure. In one example consistent with FIG. 9,acoustic sensors 18 and 20 collect A2 and P2 heart signals (102). Asdescribed above, acoustic sensors 18 and 20 may collect heart soundssignals that are then processed by a remote processor such as processor44 of programmer 24 or processor 54 of IMD 26. In some examples, theacoustic waveform collected by acoustic sensor 20 is filtered andprocessed to identify the P2 heart sound and the acoustic waveformcollected by acoustic sensor 18 is filtered and processed to identifythe A2 heart sound. Blood pressure cuff 28 collects an arterial bloodpressure (104) reading. The reading may be provided to programmer 24 viawireless link, for example. In some examples, the blood pressurereadings using blood pressure cuff 28 may be collected while patient 12is at the doctor's office. In some examples, patient 12 may have a bloodpressure cuff at home and may take blood pressure reading using cuff 28at predefined intervals. Processor 54 of programmer 24 calibrates thedetected A2 heart sound with the blood pressure reading (106). In someexamples, calibration occurs over a period of time, or under a varietyof conditions. For examples, readings may be taken while a patient is atrest and again while a patient is performing some activity. Thecollection of different blood pressure and A2 amplitude reading may aidin a more accurate patient specific calibration curve for therelationship between A2 amplitude and arterial blood pressure.

In some examples, a patient may undergo a single invasive procedure tocollect a pulmonary pressure reading form a pressure catheter (106). Thecollection of the pulmonary pressure reading is generally a done undergeneral anesthesia. A catheter is introduced into patient 12 through alarge vein such as the internal jugular, subclavian or femoral veins.The catheter is then threaded through the right atrium of heart, theright ventricle, and finally into the pulmonary artery. From thelocation in the pulmonary artery, the catheter can collect a pulmonaryartery pressure reading. Processor 44 may calibrate the P2 heart soundamplitude with the collected pulmonary pressure reading (110). Thecalibration allows for an approximation of current pulmonary pressure tobe made based on the P2 heart sound when a pressure catheter is not inplace. This in turn, allows for the tacking of a patient's pulmonarypressure with minimal invasion.

After both the A2 heart sounds and the P2 heart sounds have beencalibrated, the system, including acoustic sensors 18 and 20, maycontinue to monitor the A2 and P2 heart sounds (112). Based on thecalibration of the A2 and P2 heart sound amplitudes with actual pressurereading, programmer 24 is able to monitor the ongoing pulmonary andarterial blood pressure with minimal invasion. In some examples,processor 44 may compare the A2 amplitude to the P2 amplitude (114). Ifthe amplitude is greater than the P2 amplitude then acoustic sensors 18and 20 continue to monitor the A2 and P2 heart sounds. If the amplitudeof the P2 heart sound is greater than the A2 heart sound, then processor44 generates an indication of pulmonary hypertension (116).

FIG. 10 is a flow chart illustrating another example method consistentwith the present disclosure. Although this discussed as thoughimplemented by IMD 26 in conjunction with external patch 16. Variousportions of the method may be performed by other devices, such asprogrammer 24. In some examples, process 54 may activate acoustic sensor18 and 20 (120) based on one or more activation events. For example,acoustic sensors 18 and 20 may be activated at a certain time of day orwhen patient activity is below a certain level. Acoustic sensor 18 and20 provide wideband data collection (122). Processor 54 may triggerspecific heart sound collection based on ECG or Lung sounds (124). Forexample, activation may also be based whether patient 12 is currentlybreathing. Heart sounds may also be recorded for short intervals betweenbreaths and following the QRS portion of the ECG signal. Processor 54 orsignal analyzer 62 may set a bandpass filter for the P2 heart sound(126). Signal analyzer 62 then identifies the P2 heart sound in aselected post-QRS window (128). For the identified P2 heart sound,signal analyzer 62 then determines P2 amplitude and analyzes the splitbetween A2 and P2 heart sounds in the S2 heart sound (130). Based on theanalysis and the determination of the P2 amplitude, and the S2, signalanalyzer 62 may determine if the P2 heart sound characteristics areabove a predetermined threshold (132). If the P2 heart sound amplitudeis not above the threshold then, processor 54 may continue to monitorheart sounds signal via the acoustic sensors. If P2 amplitude is abovethe threshold (132) then the P2 heart sounds characteristics and outcomeof the threshold determination are compared with one or more heartfailure signatures (136). The heart failure signatures may be determinedbased on monitoring of patient lung sounds as well as other heart soundparameters, such as the presence of a S3 heart sound. Processor 54 thendetermines if patient 12 has pulmonary hypertension induce heart failureprogression (138). In some examples, processor 54 compares current heartfailure signatures to previous heart failure signatures to determine ifheart failure within patient 12 has progressed. For example, processor54 may compare the current amplitude of heart sound S3 to the previousamplitude of heart sound S3. If heart failure has not progressed, IMD 26may continue to monitor patient heart sounds. If patient 12 haspulmonary hypertension induced heart failure progression (138) thenprocessor 54 initiates a change in therapy (140). Initiation of a changein therapy may include alerting a physician to the change in patientstatus. In some examples, processor 54 may modify one or more therapyparameters. For example, processor 54 may change one or more pacingparameter. In some examples, processor 54 may reactivate acousticsensors 18 and 20 and again check for the presence of pulmonaryhypertension and/or progression of heart failure in order to determinethe efficacy of the changes in therapy.

FIG. 11 is a conceptual diagram illustrating an exemplary external patchconsistent with the present disclosure. External patch 16 includesdirectional acoustic sensor 18 and 20. Directional acoustic sensor 18may be oriented to pick up sound waves 150 resulting from the aorticvalve closure. Directional acoustic sensor 20 may be oriented to pick upsound waves 152 resulting from the pulmonary valve closure. In someexamples, the placement of the directional acoustic sensors 18 and 20may be on a patient chest X-ray, or results of some other imagingtechnique.

The techniques described in this disclosure may be implemented, at leastin part, in hardware, software, firmware or any combination thereof. Forexample, various aspects of the techniques may be implemented within oneor more microprocessors, digital signal processors (DSPs), applicationspecific integrated circuits (ASICs), field programmable gate arrays(FPGAs), or any other equivalent integrated or discrete logic circuitry,as well as any combinations of such components, embodied in programmers,such as physician or patient programmers, stimulators, or other devices.The terms “processor,” “processing circuitry,” “controller” or “controlmodule” may generally refer to any of the foregoing logic circuitry,alone or in combination with other logic circuitry, or any otherequivalent circuitry, and alone or in combination with other digital oranalog circuitry.

For aspects implemented in software, at least some of the functionalityascribed to the systems and devices described in this disclosure may beembodied as instructions on a computer-readable storage medium such asrandom access memory (RAM), read-only memory (ROM), non-volatile randomaccess memory (NVRAM), electrically erasable programmable read-onlymemory (EEPROM), FLASH memory, magnetic media, optical media, or thelike. The instructions may be executed to support one or more aspects ofthe functionality described in this disclosure.

Various examples have been described. These and other examples arewithin the scope of the following claims.

What we claim is:
 1. A method comprising: receiving an A2 heart soundsignal from a first external acoustic sensor; receiving a P2 heart soundsignal from a second external acoustic sensor; determining at least oneA2 heart sound signal parameter from the A2 heart sound signal;determining at least one P2 heart sound signal parameter from the P2heart sound signal; based on the at least one P2 heart sound signalparameter, estimating pulmonary arterial pressure; receiving a pulmonarypressure signal from a pressure catheter; and calibrating the at leastone P2 heart sound signal parameter with the pulmonary pressure signal.2. The method of claim 1, further comprising: comparing the at least oneA2 heart sound signal parameter and the at least one P2 heart soundsignal parameter; and determining an indication of pulmonaryhypertension based on the comparison.
 3. The method of claim 1, furthercomprising: receiving an arterial blood pressure signal from an externalblood pressure monitor; and associating the at least one A2 heart soundsignal parameter with the arterial blood pressure signal.
 4. The methodof claim 1, further comprising: determining a post QRS window; andidentifying the P2 heart sound signal occurring within the post QRSwindow.
 5. The method of claim 4, further comprising; determining one ofa time of day and a patient activity level; and activating the firstexternal acoustic sensor and the second external acoustic sensor inresponse to the determined one of a time of day and a patient activitylevel.
 6. The method of claim 1, further comprising, in response to anindication of pulmonary hypertension, generating a third set of therapyparameters.
 7. The method of claim 1, wherein the first externalacoustic sensor is oriented to receive the A2 heart sound signal and thesecond external acoustic sensor is oriented to receive the P2 heartsound signal.
 8. A method comprising: receiving an A2 heart sound signalfrom a first external acoustic sensor; receiving a P2 heart sound signalfrom a second external acoustic sensor; determining at least one A2heart sound signal parameter from the A2 heart sound signal; determiningat least one P2 heart sound signal parameter from the P2 heart soundsignal; based on the at least one P2 heart sound signal parameter,estimating pulmonary arterial pressure; determining whether an amplitudeof the P2 heart sound signal is greater than a predetermined threshold;comparing the P2 heart sound signal and a predetermined heart failuresignature; and determining pulmonary hypertension induced heart failureprogression in response to the comparing.
 9. The method of claim 8,further comprising analyzing a split between A2 heart sound and a P2heart sound in an S2 heart sound.
 10. A medical device systemcomprising: a first external acoustic sensor configured to receive an A2heart sound signal; a second external acoustic sensor configured toreceive a P2 heart sound signal; a processor configured to: determine atleast one A2 heart sound signal parameter from the A2 heart soundsignal, determine at least one P2 heart sound signal parameter from theP2 heart sound signal, and estimate pulmonary arterial pressure inresponse to the at least one P2 heart sound signal parameter; anexternal blood pressure sensor; and a telemetry module configured toreceive an arterial blood pressure signal from external blood pressuresensor, wherein the processor is further configured to associate the atleast one A2 heart sound signal parameter with the arterial bloodpressure signal.
 11. The system of claim 10, wherein the processor isfurther configured to compare the at least one A2 heart sound signalparameter and the at least one P2 heart sound signal parameter, andprovide an indication of pulmonary hypertension based on the comparison.12. The system of claim 10, wherein the processor is further configuredto, in response to an indication of pulmonary hypertension, generate athird set of therapy parameters.
 13. A medical device system comprising:a first external acoustic sensor configured to receive an A2 heart soundsignal; a second external acoustic sensor configured to receive a P2heart sound signal; a processor configured to: determine at least one A2heart sound signal parameter from the A2 heart sound signal, determineat least one P2 heart sound signal parameter from the P2 heart soundsignal, and estimate pulmonary arterial pressure in response to the atleast one P2 heart sound signal parameter; a pressure catheter; and atelemetry module configured to receive a pulmonary pressure signal fromthe pressure catheter, wherein the processor is further configured tocalibrate the at least one P2 heart sound signal parameter with thepulmonary pressure signal.
 14. A medical device system comprising: afirst external acoustic sensor configured to receive an A2 heart soundsignal; a second external acoustic sensor configured to receive a P2heart sound signal; a processor configured to: determine at least one A2heart sound signal parameter from the A2 heart sound signal, determineat least one P2 heart sound signal parameter from the P2 heart soundsignal, and estimate pulmonary arterial pressure in response to the atleast one P2 heart sound signal parameter, wherein the processor isfurther configured to determine determining a post QRS window, andidentify the P2 heart sound signal occurring within the post QRS window.15. The system of claim 14, wherein the processor is further configuredto determine one of a time of day and a patient activity level, andactivate the first external acoustic sensor and the second externalacoustic sensor in response to the determined one of a time of day and apatient activity level.
 16. A medical device system comprising: a firstexternal acoustic sensor configured to receive an A2 heart sound signal;a second external acoustic sensor configured to receive a P2 heart soundsignal; a processor configured to: determine at least one A2 heart soundsignal parameter from the A2 heart sound signal, determine at least oneP2 heart sound signal parameter from the P2 heart sound signal, andestimate pulmonary arterial pressure in response to the at least one P2heart sound signal parameter, wherein the processor is furtherconfigured to determine whether an amplitude of the P2 heart soundsignal is greater than a predetermined threshold, compare the P2 heartsound signal and a predetermined heart failure signature, and determinepulmonary hypertension induced heart failure progression in response tothe comparing.
 17. The system of claim 16, wherein the processor isfurther configured to analyze a split between A2 heart sound and a P2heart sound in an S2 heart sound.
 18. A non-transitory computer-readablemedium comprising instructions for causing a programmable processor to:receive an A2 heart sound signal from a first external acoustic sensor;receive a P2 heart sound signal form a second external acoustic sensor;determine at least one A2 heart sound signal parameter from the A2 heartsound signal; determine at least one P2 heart sound signal parameterfrom the P2 heart sound signal; estimate pulmonary arterial pressure inresponse to the at least one P2 heart sound signal parameter; determinewhether an amplitude of the P2 heart sound signal is greater than apredetermined threshold; compare the P2 heart sound signal and apredetermined heart failure signature; and determine pulmonaryhypertension induced heart failure progression in response to thecomparing.